On Thursday 05 February 2009 07:09:15 Christoph Lameter wrote:> On Wed, 4 Feb 2009, Nick Piggin wrote:> > That's very true, and we touched on this earlier. It is I guess> > you can say a downside of queueing. But an analogous situation> > in SLUB would be that lots of pages on the partial list with> > very few free objects, or freeing objects to pages with few> > objects in them. Basically SLUB will have to do the extra work> > in the fastpath.>> But these are pages with mostly allocated objects and just a few objects> free. The SLAB case is far worse: You have N objects on a queue and they> are keeping possibly N pages away from the page allocator and in those> pages *nothing* is used.

Periodic queue trimming should prevent this from becoming a big problem.It will trim away those objects, and so subsequent allocations will comefrom new pages and be densely packed. I don't think I've seen a problemin SLAB reported from this phenomenon, so I'm not too concerned about itat the moment.